1. Field of the invention
The present invention relates to a method and apparatus for encoding telecine-converted video data for seamless connection and, more particularly to a bitstream for use in an authoring system for variously processing a data bitstream comprising the video data, audio data, and sub-picture data constituting each of plural program titles containing related video data, audio data, and sub-picture data content to generate a bitstream from which a new title containing the content desired by the user can be reproduced, and efficiently recording and reproducing said generated bitstream using a particular recording medium.
2. Description of the prior art
Authoring systems used to produce program titles comprising related video data, audio data, and sub-picture data by digitally processing, for example, multimedia data comprising video, audio, and sub-picture data recorded to laser disk or video CD formats are currently available.
Systems using Video-CDs in particular are able to record video data to a CD format disk, which was originally designed with an approximately 600 MB recording capacity for storing digital audio data only, by using such high efficiency video compression techniques as MPEG. As a result of the increased effective recording capacity achieved using data compression techniques, karaoke titles and other conventional laser disk applications are gradually being transferred to the video CD format.
Users today expect both sophisticated title content and high reproduction quality. To meet these expectations, each title must be composed from bitstreams with an increasingly deep hierarchical structure. The data size of multimedia titles written with bitstreams having such deep hierarchical structures, however, is ten or more times greater than the data size of less complex titles. The need to edit small image (title) details also makes it necessary to process and control the bitstream using low order hierarchical data units.
It is therefore necessary to develop and prove a bitstream structure and an advanced digital processing method including both recording and reproduction capabilities whereby a large volume, multiple level hierarchical digital bitstream can be efficiently controlled at each level of the hierarchy. Also needed are an apparatus for executing this digital processing method, and a recording media to which the bitstream digitally processed by said apparatus can be efficiently recorded for storage and from which said recorded information can be quickly reproduced.
Means of increasing the storage capacity of conventional optical disks have been widely researched to address the recording medium aspect of this problem. One way to increase the storage capacity of the optical disk is to reduce the spot diameter D of the optical (laser) bean. If the wavelength of the laser beam is 1 and the aperture of the objective lens is NA, then the spot diameter D is proportional to 1/NA, and the storage capacity can be efficiently improved by decreasing 1 and increasing NA.
As described, for example, in U.S. Pat. No. 5,235,581, however, coma caused by a relative tilt between the disk surface and the optical axis of the laser beam (hereafter "tilt") increases when a large aperture (high NA) lens is used. To prevent tilt-induced coma, the transparent substrate must be made very thin. The problem is that the mechanical strength of the disk is low when the transparent substrate is very thin.
MPEG1, the conventional method of recording and reproducing video, audio, and graphic signal data, has also been replaced by the more robust MPEG2 method, which can transfer large data volumes at a higher rate. It should be noted that the compression method and data format of the MPEG2 standard differ somewhat from those of RPEG1. The specific content of and differences between MPEG1 and MPEG2 are described in detail in the ISO-11172 and ISO-13818 MPEG standards, and further description thereof is omitted below.
Note, however, that while the structure of the encoded video stream is defined in the MPEG2 specification, the hierarchical structure of the system stream and the method of processing lower hierarchical levels are not defined.
As described above, it is therefore not possible in a conventional authoring system to process a large data stream containing sufficient information to satisfy many different user requirements. Moreover, even if such a processing method were available, the processed data recorded thereto cannot be repeatedly used to reduce data redundancy because there is no large capacity recording medium currently available that can efficiently record and reproduce high volume bitstreams such as described above.
More specifically, particular significant hardware and software requirements must be satisfied in order to process a bitstream using a data unit smaller than the title. These specific hardware requirements include significantly increasing the storage capacity of the recording medium and increasing the speed of digital processing; software requirements include inventing an advanced digital processing method including a sophisticated data structure.
Therefore, the object of the present invention is to provide an effective authoring system for controlling a multimedia data bitstream with advanced hardware and software requirements using a data unit smaller than the title to better address advanced user requirements.
Connecting a media player for reproducing the title content contained in such multimedia data to a television receiver so that a user can easily access and use the reproduced information is also desirable. Movies and other materials originally recorded on film will also be commonly used as the source titles. When the bitstream is generated for recording, digital VCRs are used to supply the title content to the recording signal generator because of the ease of editing. Title content, such as movies, recorded on film must be converted to a video format by means of a frame rate conversion process, called "tele-cine conversion," and this frame-converted signal is then used to produce the recording signal.
"Tele-cinema" conversion basically accomplishes the frame rate conversion by inserting at a regular period a redundant field copying a field with the same parity. Because there is not a simple integer ratio between the film frame rate and video frame rate, a conversion pattern that differs from the normal pattern is inserted to the gaps in this regular insertion process. When the resulting tele-cine converted signal is then compression coded, the copied redundant fields will also be coded if compression coding is applied at the video frame rate. Coding redundant field information is obviously inefficient. As a result, compression coding is applied after a reverse telecine conversion process whereby the copied redundant fields are detected and removed. In this case, a flag indicating whether a redundant field has been removed, and a flag defining the presentation order of the two fields in the frame, are both recorded with each frame.
However, when the video objects VOB for plural title editing units to which this reverse tele-cine conversion process has been applied are connected and reproduced, the top field continues at the seam between the contiguously reproduced VOB. MPEG decoder behavior is not generally guaranteed in such cases. In a DVD player, a field may be inserted or deleted, resulting at best in incoherent image reproduction and at worst in the insertion of a completely unrelated, and therefore meaningless, field. Even in the best-case scenario, i.e., incoherent image reproduction, synchronization with the audio may be lost. As a result, true seamless reproduction cannot be achieved.
Therefore, the object of the present invention is to provide a data structure whereby seamless reproduction can be achieved even at cell borders without the bottom fields from two connected frames or the top fields from two connected frames being connected when video objects VOB are seamlessly reproduced; a method for generating a system stream having said data structure; a recording apparatus and a reproduction apparatus for recording and reproducing said system stream; and an optical disk medium and optical disk recording method for recording said system stream.
The present application is based upon Japanese Patent Application No. 7-252733, which was filed on Sep. 29, 1995, the entire contents of which are expressly incorporated by reference herein.